The present invention relates to a rollover-sensing system and method for determining fast roll events, such as curb-tripped rollover events and slow roll events, such as soil-tripped rollover events, for a vehicle. The events are used to control side airbag inflatable curtains and seat belt pretensioners.
There are different types of rollover events. A vehicle can be involved in either an upward rollover event or a downward rollover event when the vehicle is traveling in a forward direction. A vehicle can be involved in an un-tripped rollover event when the vehicle is traveling and tilting beyond its stability angle.
A vehicle can be involved in a tripped rollover event when the vehicle is sliding laterally and hits an obstacle. For example, a vehicle can be involved in a soil- or curb-tripped rollover event. A soil-tripped or slow rollover event occurs when the vehicle is initially traveling on a roadway, and begins a slide that takes the vehicle off the roadway. As the vehicle slides off the roadway, the wheels of the vehicle may contact unpaved ground, grass, or soil. Soil may build up near the wheels of the vehicle and create a lip or mound of soil. The mound may reach a sufficient size or configuration such that it acts as a barrier over which the wheels and, consequently, causes lateral acceleration that results in a soil-tripped rollover event. A fast or curb-tripped rollover event occurs when the vehicle is initially traveling on a roadway, and then slides sideways into impact by a wheel or wheels with a curb that acts as a barrier over which the wheels and, consequently, causes a lateral acceleration greater than during a slow roll event resulting in a curb-tripped rollover event. In such a case, a lateral impact force is typically exerted against an obstacle, such as a curb, is stronger than that of a soil-tripped event.
One prior art arrangement uses a time threshold to inhibit late airbag deployment. The arrangement includes only one timer for both soil and trip curbs. The time based arrangement is not favored for various reasons. An object of the invention is to provide an arrangement for determining and differentiating slow roll events and fast roll events. For slow roll events, only a pre-tensioner is operated. For fast roll events, the pre-tensioner is operated and a side airbag inflatable curtain is deployed.